Method of forming resistor assemblies



Feb. 24, 1953 J. MARSTEN ETAL 2,629,166

METHOD OF FORMING RESISTOR ASSEMBLIES Filed 001;. 7, 1948 2 SHEETS--SHEET 1 FIG. 2.

lhmentots JESSE MARSTEN ALEXANDER L. PUGH JR.

6.4 6 4i: M. FIG. u. 83 FIG. l2.

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Feb. 24, 1953 Filed Oct. 7. 1.94s

INPUT Patented Feb. 24, 1953 METHOD OF FORMING RESISTOR ASSEMBLIES Jesse Marsten, Carroll Park, and Alexander L.

Pugh, Jr., Bala-Cynwyd, Pa., assignors to International Resistance Company, Philadelphia, Pa., a corporation of Delaware Application October 7, 1948, Serial No. 53,358

4 Claims.

This invention relates to electrical resistance units and resistance network assemblies; more particularly, this invention relates to the production of various kinds of resistance units and electrical circuits formed by reactance units connected in series and in parallel.

An object of this invention is to provide for the production of electrical resistance units and reactance circuit assemblies in a manner so as to meet the most rigorous standards of quality at minimum cost. A further object is to provide for the production of resistance units and reactance assemblies having extremely uniform electrical characteristics and yet of minimum size and of such structure as to stand up under severe conditions of use. A further object is to provide for the production of the above by processes which include steps, such as coating and stamping whereby maximum use may be made of largescale mass production techniques. A still further object is to provide for carrying out the above in such a manner that relatively complicated electrical circuits may be manufactured without the use of connecting wires and electrical connecting techniques such as soldering. A further object is to provide an arrangement whereby resistance units or assemblies may be manufactured by simple process steps with each unit or assembly including two or more resistors having the same or different resistance values which are accurately determined. Further objects are to provide resistance units or assemblies and electrical circuits of the character referred to above and to provide processes for producing the same in an efiicient and dependable manner. These and other objects will be in part obvious and in part pointed out below.

' The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts and in the several steps and relation and order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

In the drawings which show a number of embodiments of the invention:

Figure l is a top plan view of a strip of coated plastic sheet material from which resistor units or blanks are to be cut;

Figure 2 is a top plan view of a resistor unit or blank after being cut from the strip of Figure 1;

Figures 3 and 4 are top plan views of completed resistor units or assemblies made from blanks such as that of Figure 2;

Figure 5 is similar to Figure 1 and shows another strip of coated plastic sheet material;

Figures 6 and 7 are similar to Figures 3 and 4 and show resistor assemblies produced from a sheet such as that of Figure 5;

Figures 8, 9 and 10 correspond respectively to Figures 5, 6 and 7 and show another embodiment of the invention;

Figure 11 is a top plan view on reduced scale of a resistor assembly similar to that of Figure 10;

Figure 12 is a bottom plan view of the resistor assembly of Figure 11;

Figures 13 and 15 are similar to Figure 8 and show strips for producing other embodiments of the invention;

Figures 14 and 16 show resistor assemblies produced respectively from the strips of Figures 13 and 15; and

Figure 1'7 is a schematic circuit diagram of the assembly of Figure 16.

Referring particularly to Figure 1 of the drawings, there is shown a thin sheet 2 of insulating material in the form of phenol-resin or Bakelite and having on its top surface a coating of resistance material 4 which is graphite or other carbon deposited with a varnish binder and then baked. In this embodiment the coating 4 is applied by a rubber roller but, under some circumstances, it is applied by spraying, by painting or by stamping. The strip 2 with its coating t has punched from it disks or blanks 6, indicated in broken lines, one of which is shown in Figure 2.

Each disk then is provided with conducting termination coatings, for example, silver coatings in the form of an outer annulus 8 and a central disk or annulus Ill. These termination coatings are formed by spraying on a coating of varnish containing silver flakes and thereafter baking again. The disk of Figure 2 is then placed in an indexing machine which scrapes the coatings 4 and 6 from the disk along a plurality of spaced radial lines so as to expose the bare insulation material along radial strips I2. Thus, between the central annulus l and each sector of the outer annulus B, there is a resistance unit or resistor l3 formed by a sector of the resistance coating 4. A central electrical terminal I4 is then attached by a rivet l5 to the center of the disk and each sector of the annulus 8 has an electrical terminal l6 attached by a rivet IT. For these rivets iii and I1 each disk 6 has punched into it a central rivet hole l9 and appropriate outer rivet holes l8. These holes are punched simultaneously with the stamping of the disks from strip 2 and therefore the silver termination coatings will, to an extent, form beads down into the tops of the holes. In this way good electrical contact is insured between each electrical terminal and its rivet and the adjacent silver termination coating.

In the embodiment of Figure 3, the bare radial strips l2 are angularly equidistant from each oth er and they are of uniform width throughout. Therefore, the various resistors 53 have the same resistance values. The central terminal I4 is a common terminal for all the resistors, and it has a tab projecting upwardly to permit easy soldering. Each resistance section then has its own terminal l6 projecting radially outwardly so that the terminals are all spaced from each other a substantial distance and this has advantages during installation and use. Thus, a sturdy, high quality resistor is provided wherein the resistors occupy minimum space and are held rigidly in spaced relationship. In this embodiment the rivet l5 which holds terminal id in place is an eyelet which performs the additional function of attaching the disk to a mounting chassis (not shown).

In Figur 4 the various resistors have different resistance values; this result is obtained by so adjusting the indexin machine that there are different angular spacings between the various bare strips l2. Disks such as that of Figure 2 are used for producing the resistor assembly of Figures 3 and 4; in Figure 3 six resistors are provided while in Figure .i there are only four resistors. In Figure 4, the largest resistor 2i has two connecting terminals, and as shown at the bottom of the figure, the resistance and termination coatings are scraped away from the lower hole 20 so that the disk may be mounted upon a metal bracket without the necessity for providing auxiliary insulation means. Also, the electrical terminals may be equally spaced from each other even though the resistance sections have different resistance values, but if desirable, the terminals may be so spaced that each is connected centrally of its termination coating sector or in any other convenient way.

As indicated above, coating 4 is formed by depositing a thin layer of varnish containing graphite or other carbon particles and then baking. The resistance value of the resistors thus formed is raised if there is less carbon in the varnish, and the resistance value is reduced if there is more carbon. Furthermore, within certain limits the resistance value depends upon the degree of baking; 1. e., a certain minimum baking gives a relatively high resistance value, and the resistance value decreases as the baking continues. Thus, the resistance values may be controlled as desired during manufacture and extremely uniform products are produced; and after the baking operation has been completed the resistance value is constant. Throughout the drawings the relatively heavier shadings of 4 the resistance coatings indicate correspondingly lower relative resistance values, and vice versa.

The production of resistors such as those of Figures 3 and 4 is carried on largely with automatic machinery; first the resistance coating is deposited and baked on sheet 2, and thereafter the disks are stamped out with the terminal or rivet holes and the termination coatings 8 and 18 are applied.

The coatings are then scraped oiT along strips 22 an indexing machine which operation is also automatic. It has been indicated that the resistance value of the resistance coating may be varied by changing the amount of carbon in the coating and also by changing the time of baking, and the number of resistors and the specific resistance values of the various resistors may be changed by changing the adjustment of the indexing machine. Therefore, a production line may produce a wide variety of resistor assemblies having vastly different characteristics, and it is a relatively simple matter to change the characteristics of the resistor assemblies without modification of the procedure of manufacture. Thus, it is possible to produce a multiple number of resistors on one base suitably interconnected, and these are produced with a minimum number of operations. The resistance material and the conductive termination coatings may be applied simultaneously in one operation, and a single stamping operation may produce the multiple resistors and also cut the assembly from the main strip. In addition to the advantages in production of resistor assemblies in accordance with the present invention, there is the additional feature that a resistor assembly may be handled and assembled into an electrical circuit with much less work and expense than would be involved if the equivalent number of separate resistors were used.

In Figure 5 there is shown a strip 22 which is identical with strip 2 and which has five separate strips of the resistance coating of the type of coating :2 which are applied simultaneously and continuously. After being coated and baked, strip 22 is cut into predetermined lengths to form resistor assemblies such as assembly 26 of Figure 6. At the left-hand side in Figure 6, sheet 22 is provided with a silver termination coating 28 of the same type as coating 8, and it is punched to provide a hole 38 for the attachment of an electrical terminal. At the righthand side of the figure, each of the resistance coating strips 24 is provided with a similar termination coating 32, and a hole Ed is provided for the attachment of an electrical terminal.

Thus the resistor assembly 26 is a base of insulating material which carries five resistors each connected at one end to a common terminal and connected respectively to separate terminals at the other ends. The widths and thicknesses of strips 24 may be the same with the result that the resistance values of the various resistors are the same and in this way the assembly of Figure 6 may be electrically similar to that of Figure 3. However, in Figure 6 the various strips 24 have different widths so that they have different resistant values and therefore the assembly corresponds more nearly to the assembly of Figure 4. Holes 30 and 34 may be punched simultaneously with the cutting of sheets into lengths.

As indicated above, the resistance value of a resistor of this type may be varied by changing the relative amount of carbon in the resistance hole 46.

coating. Therefore, as shown in Figure '1 an assembly 35, similar to Figure 6, has five resistance strips of the same width but having different amounts of carbon in the coatings forming them. Thus, in figure 7 the resistors 36, 31, 38, 39 and 40 have different resistance values. For example, the center resistor 39 has a relatively small amount of carbon in it so that it has a high resistance value, whereas the next lower resistor 39 has a greater amount of carbon in it so that it has a relatively low resistance value. At the lefthand side of Figure 'I, the assembly has a termination coating strip which is divided into two coatings 4| and 42; the upper three resistors 36, 31 and 36 are connected to one coating 4| and have a common terminal at an opening 43, and the two lower resistors 39 and 40 are connected to coating 42 and have a common terminal at an opening 44. At the right, each resistor has a termination coating 45 and a terminal Thus the resistor assembly 35 includes two electrically independent multiple resistor units or resistance networks.

In the embodiment of the invention of Figures 8, 9 and 10, a sheet or strip 41 of insulation material is first covered with a resistance coating 48 and baked, the same as in Figure 1, and then at the two sides of the strip there is applied high conductivity termination coatings 49 and 50 illustratively, silver or other low resistance material such as copper or graphite. The low resistance termination coatings may be applied simultaneously with the resistance coating 48. Contact between the termination coatings and the resistance coating results automatically from the merging or fusing of the coatings together. After suitable baking as outlined above, the strip is cut into predetermined lengths and is simultaneously punched to form units 5I having terminal attaching holes 52 and 53 therethrough. Coatings 48 and 50 are then scraped off along five parallel strips 54 to expose sheet 41 and separate coatings 48 and 50 into spaced areas. This forms five resistors 55 of equal width and the same resistance values and with one common terminal at hole 52 and separate terminals at holes 53. In Figure the resistors have different widths and have different resistance values. In the embodiment of Figure 10, the resistors have different resistance values. Furthermore, the termination coating is divided to form two resistors at the left which have a common terminal at hole 56, two adjacent resistors also have a common terminal at a hole 58, and a righthand resistor having a terminal at a hole 60. At the bottom there are five holes 62, each for a terminal for one of the resistors.

In the embodiment of the invention of Figures 11 and 12, an arrangement similar to that of Figure 10 is shown wherein remote resistors are connected together by coatings on the back of the sheet. Five resistors 55, 51, 59, SI and 53 having different resistance values are formed on a sheet II in accordance with the technique of Figures 8 to 10 with resistors 55 and 51 having a common terminal at their lower ends. Upon the bottom or rear side of the insulation sheet there is at the top a U-shaped strip of silver flake coating 13 which extends from immediately behind the upper end of resistor 51 to immediately behind the upper end of resistor 6|. At the bottom of the sheet there is an inverted U-shaped coating which extends from immediately beneath the lower end of resistor 59 to immediately beneath the lower end of resistor 63. Thus by connecting an eyelet through each of holes 11 and 19 a connection is made between the upper ends of resistors 51 and 59; and by connecting eyelets through each of two holes 8| and 83, a similar connection is made between the lower ends of resistors 59 and 63. Thus two electrical resistor networks are provided wherein the front side of the sheet of insulating material is the carrier for the resistors while the back side of the sheet is the carrier for additional electrical circuit connections.

The embodiments of Figures 13 to 17 are similar to those of Figures 8 to 12 and differ therefrom mainly in that the resistors are formed by punching out portions of the sheet material where the coatings are to be removed rather than scraping oif the coatings to form the resistors. In Figure 13 a strip of sheet plastic 64 has a resistance coating 66 which is applied in the manner of Figure 8 except that the two border strips 65 and 61 of the sheet material are left bare. Silver termination strip coatings 68 and 69 are then applied overlaying the edges of the resistance coating 66. Thus the coated sheet of Figure 13 is similar to that of Figure 8 except that there are the two uncoated border strips along the sides of the termination coatings.

The cutting and punching operation then is performed and this cuts the strip 64 into predetermined lengths or sheets 10 each of which is punched with an appropriate number of terminal holes 12; this operation also punches out five transverse slots or openings 14, 16, 18 and 80. Slot 14 extends completely across the width of coatings 66, 68 and 69 and terminates at its ends in the uncoated border strips 65 and 61. Thus slot 14 forms a resistor 82 which has terminal holes 12 at its ends. Slot 16 terminates at its upper end at border strip 65 and at its lower end at coating 69, and slot 18 is identical with slot 14. Thus, slot 16 forms with slot 14 a resistor 84, and forms with slot 10 a resistor 86. At their upper ends, resistors 84 and 85 have separate terminal holes while at their lower ends they have a common terminal hole. Slot 80 is identical with slot 16 and therefore forms two resistors 88 and which have separate terminal holes at the top of the figure and a common terminal hole at the bottom. Resistors 84 and 86 are of the same width and have the same resistance value; whereas, resistor 88 is narrower than resistor 90 and has a higher resistance value.

The embodiment of Figures 15 to 17 is similar to that of Figure 14 and is a complete circuit of all of the resistors with the interconnections to form a two-stage vacuum tube resistance coupled amplifier. A strip 92 of sheet material has a resistance coating 94 at the upper margin of which is a strip of silver termination coating 96. At the lower edge of coating 94 there is a cimilar strip of silver termination coating 98 and beneath this is a strip of similar coating I00 which is separated from strip 98 by an uncoated strip I02 of the sheet. Strip 92 is coated in this manner and properly baked as outlined above, and then in a single stamping operation it is cut into lengths I03 and punched to form openings as shown in Figure 16.

Along the top of Figure 16, each length I03 has an uninterrupted strip of termination coating 95 which has a terminal hole 98, and connected to coating 96 is the upper end of each of four resistors I06, I08, H0 and H2. Positioned aeearec at the left hand side of the unit is an inverted U-shaped resistor H4, and positioned between resistors I06 and it; is a similar resistor llfi. Resistor H4 is formed by a slot i i! and an elongated narrow slot H3. Slot H8 extends between the legs of the resistor and terminates at its lower end in the uncoated strip 162 and at its upper end a substantial distance below coating 96. Slot H"! terminates at the end of the U in the uncoated strip {32 and extends along the side of the resistor Ht. Resistor lit is formed by a somewhat similar set of slots; i. e., an inverted U-shaped slot E28 and a central slot I22. Resistor I08 is formed by the righthand side of slot lilli and (at the right) by a slot i223 which terminates at its lower end in a reduced portion at the uncoated strip tell, extends up to coating 53. Resistor ill) is formed by slot I24 and a similar slot 22% which also forms resistor H2.

The righthand end portion oi coating illil is formed into a separate termination coating lit by a slot 139 extending from the bottom edge of the sheet upwardly to the uncoated strip lbs This righthand coating i213 has a terminal hole I32, and the main portion of coating it'll? has a hole 134. Resist-or H has a pair of holes ltd and I33; and, resistor H6 has a pair of holes Mil and I42. Resistors Hit, tilt, Md and HE have their upper ends connected to hole Sit and they have at their lower ends, respectivel holes hi6, I43, 150 and I52. As indicated above, the assembly of Figure 16 is for a two stage vacuum tube resistance coupled amplifier. For this purpose, there are four capacitors connected as fol lows: a capacitor itl l connected between the lower end of resistor Hi6 and the lo- .nd end of resistor H6; capacitor 650 connected betwee the righthand end of resistor Hi3 and the lower end of resistor W8; capacitor connected between the lower end of resistor lit and coating I00; and, a capacitor Iiiti connected between the lower end of resistor iii? and the righthand coating I28.

In Figure l"! the schematic diagram of tl-e amplifier circuit includes two vacuum tubes s and 16 2' connected to the various elements of the circuit of the assembly of Figure 15. In

completing the amplifier from the assembly of Figure 16 it is only necessary to connect the sockets for tubes i623 and it' l to the appropriate terminal holes as indicated in Figure 17. Thus an amplifier of extremely rugged construction is provided which is compact and light in weight and which is mass-produced at a cost far b low the cost of a comparable amplifier of the prior construction. The thin flat sheet of plastic material sufficient rigidity to withstand considerable abuse and it fits snugly along the side of a small case for batteries or the like. No auxiliary supporting plate need be provided for the resistors and this saves weight and space. Furthermore, the elimination of connecting wires and solder joints gives a construction of superior quality and performance.

As indicated above, the production facilities such as those which are used in producing the resistor assemblies of Figures 3 and are also adaptable to the production of resistors such as those shown in the other figures. it has been indicated that the resistance value of resistors is decreased by increasing the amount of carbon in the resistance coating and within certain limits the resistance is decreased by increasing the time of baking.

.Thus, the coating and baking equipment is adiusted to produce any specific :form of resistance coated plastic sheets of uniform quality. Furthermore, strips of resistance coatings of different widths may be applied to a sheet as in Figure 5, or difierent coatings may be applied simul taneously to a sheet as in Figure 7. The termination coatings may :be deposited by stamping or by other processes depending upon the particular demands of production. Under some circumstances a number of standardized resistance coated sheets may be produced and then these sheets may be fabricated into such widely varying forms as the embodiments of Figures 3, 4, 9 to 12, 14 and 16. Under such circumstances the same dies may be used with sheets having difierent resistance coatings so as to produce resistor assemblies having different resistance values As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied various parts all with out departing from the scope of the invention, it is to be understood that all matter hereinabove set forth, or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

We claim:

1. In the art of continuously forming assemblies of separate iixed resistors some of which are electrically connected, the steps of applying resistance material to a surface of a dielectric sheet to form a continuous resistance coating, and applying termination coatings to spaced portions or said sheet to form a continuous electrica1 contact with said resistance coating, and removing portions 0r" said resistance material and the termination coating according to a predetermined pattern to form a plurality of terminals and separate areas of resistance material connected therewith and dimensioned to achieve the resistance value desired each resistor in each assembly, thereby to form a plurality of separate resistors from the resistance coating which may be connected in a desired circuit.

The art defined by claim 1 in which the sheet is a disc with the termination coatings applied at the center and adjacent the peripheral edge thereof while the coatings are removed along substantially radial lines.

3. The art defined by claim 1 wherein the coatare r moved by punching the sheet.

42. In the art of continuously forming assemblies of separate fixed resistors some or which are electrically connected, the steps of continuously applying resistance material on a dielectric strip to form a continuous resistance coating, applying spaced longitudinal strips of termination coatings to form continuous electrical contact with said resistance coating therebetween, and removing portions of said resistance material and termination coatings along lines between said termination coatings according to a predetermined pattern to form a plurality of terminals and separate transverse resistance strips connected therewith, each strip being of a width to achieve the resistance value desired for each resistor in each assembly thereby to form a plurality of separate resistors which may be connected in a desired circuit.

JESSE MARSTEN. ALEXANDER L. PUGH, J R.

(References on following page) Name Date Swartz et a1 Sept. 4, 1934 Haroldson Dec. 18, 1934 Stoekle June 25, 1935 Arlt Jan. 5, 1937 Fruth Oct. 24, 1939 Watson June 14, 1949 Sargrove July 5, 1949 FOREIGN PATENTS Country Date Great Britain Oct. 11, 1938 OTHER REFERENCES 15 Printed Circuit Techniques--Natl Bur. of

Standards Cir. No. 468-pp. 12-15.

REFERENCES CITED Number The following references are of record in the 1,972,411 file of this patent: UNITED STATES PATENTS 5 1 ,5 Number Name Date 2,177,484 535,321 Delany Mar. 5, 1895 2,473,183 1,256,599 Schoop Feb. 19, 1918 2,474,988 1,352,934 Amt-zen et a1. 1 Sept. 14, 1920 1,586,433 Wittstein May 25, 1926 10 1,588,513 Backus July 10, 1928 Number 1,676,745 Pickard July 10, 1928 493,607 1,767,785 Stoekle June 24, 1930 1,776,955 Sheras Sept, 30, 1930 1,820,240 Michell Aug. 25, 1931 1,932,138 Kimbrough Oct. 24, 1933 

